Photobiology is the scientific study of the interactions of light with living organisms. The field includes the study of photosynthesis, photomorphogenesis, visual processing, circadian rhythms, bioluminescence, and ultraviolet radiation effects. Rather than focusing on the effects of natural light I am more interested in the physiological effects of artificial light and how this interrupts the Photoperiod Effect (plant and animal response to length of day and night). During my research I have come across a number of journals on the internet that deal with this area of study. The Influence of Incandescent Light on Reproductive and Physiological Responses of Bovine Bulls as carried out by J.D. Roussel is an experiment in which a number of bulls were exposed to 14 hours of artificial light a day while the rest of the herd continued to graze under natural illumination. The results showed that an increase in exposure to light produced a greater reproductive response that Roussel put down to an increase in germ cell production within the animals. He found that in some way the thyroidal activity was altered which indirectly affected semen quality and other metabolic functions. By altering the natural circadian rhythm of day and night, biological and physiology changes occured.

Further Research includes;

Some Effects of The Photoperiod on Development of the Impatiens Balsamea – J. Perry Austin

Prepartum Photoperiod Effect on Milk Yield and Composition in Dairy Cows – Y. Aharoni, A. Brosh, and E. Ezrat

Effects of Artificial Ultraviolet Light Exposure on Reproductive Success of the Female Panther Chameleon (Furcifer pardalis) in Captivity – G. W. Ferguson, W. H. Gehrmann, T.C. Chen, E.S. Dierenfield, and M.F. Holick

Extraretinal Photoreception during the Gonadal Photorefractory Period in the Golden-crowned Sparrow
– Fred W. Turek (below)


Extraretinal photoreception is involved in the perception of light used to measure photoperiodic time during the initiation of gonadal growth in a number of birds. Evidence is presented which demonstrates that extraretinal photoreeeptors are also involved in measuring photoperiodic time during the gonadal photorefractory period in the golden- crowned sparrow (Fig. 3). Untreated sparrows were able to terminate the refractory condition while being exposed to long dim days (16DL:8D; DL–~0.2 lux). However, birds which had their head feathers clipped to allow more light to penetrate through to the brain were main- rained in the refractory state under the same lighting conditions. These results demonstrate that extraretinal photoreception is involved in the maintenance of photorefractoriness in birds.

It has been suggested that the eyes and extraretinal photoreceptors may both be involved in the initiation of gonadal growth in golden-crowned sparrows (Gwinner et al., 1971). This conclusion was based on the observation that a reduced rate of gonadal growth occurred in sparrows with shielded brains as compared to unshielded controls when both groups of birds were exposed to the same light treatment (i.e. 16L:8D; L=6 lux). The results presented here suggest that at a light intensity of 6 lux, light may have been reaching extraretinal photoreceptors even in birds with shielded brains. Therefore, the eyes may not be involved in testicular recrudescence in this species.

This level of research into the effects of prolonged artificial light is increasing dramatically within our current medical health care system as new developments reveal the dangers of disrupting cyclical photoperiodism. It is this biological approach to photoreception in living organisms that my film will attempt to question and explore.


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